In recent years, developments within the field of nuclear medicine have introduced a new dimension to diagnostic cardiology in that radiopharmaceuticals are now used to study myocardial functions using scintigraphy. The function and viability of the heart can now be visualized at rest or under stress without using invasive surgical techniques and with no discomfort or great expense to the patient. The most common radionuclides now in use or under investigation are thallium-201, potassium-43, and various isotopes of rubidium.
Rubidium, an alkali metal analogue of potassium and similar in its chemical and biological properties, is rapidly concentrated by the myocardium. Recent advances in isotope production and instrumentation suggest that the short-lived radionuclide, rubidium-82, is the agent of choice for myocardial imaging as well as for circulation and perfusion studies.
The preferred source of rubidium-82 is from its parent, strontium-82, which can be produced in a cyclotron via rubidium-85 or by the spallation reaction of high energy protons on a molybdenum target. the short half-life of rubidium-82 (75 seconds) makes it necessary to generate rubidium-82 at the location at which it is to be used. This is accomplished using what is known as a parent-daughter radionuclide generator wherein the parent is strontium-82 (half-life 25 days) and the daughter is rubidium-82. Due to the relatively long half-life of strontium-82, it is possible to manufacture a strontium-82rubidium-82 generator, ship it to the user, and have the user elute rubidium-82 as needed.
The physical configuration of a parent-daughter radionuclide generator is well known in the art. In simple terms, it consists of a system comprising a container which holds a support medium onto which is adsorbed the parent radionuclide, inlet means for receiving eluant and outlet means for removing eluate containing the daughter radionuclide.
The prior art dicloses several materials which have been used as a support medium for strontium-82/rubidium-82 generator. U.S. Pat. No. 3,953,567, issued Apr. 27, 1976, discloses a generator utilizing as a support medium a 100-200 mesh resin which is composed for a styrene-divinyl-benzene copolymer with attached immunodiacetate exchange groups. Yano et al., J. Nucl. Med., 20 (9):961-966 (1979), disclose a generator utilizing as a support medium alumina. U.S. Pat. No. 4,400,358, issued Aug. 23, 1983, discloses a generator utilizing as a support medium hydrated, unhydrated and mixtures of the hydrated and unhydrated and mixtures of the hydrated and unhydrated forms of tin oxide, titanium oxide and ferric oxide, and unhydrated polyantimonic acid.